Problem: $ { {5} \times \left[\begin{array}{rrr}{2} & {0} & {4} \\ {1} & {4} & {-1}\end{array}\right] = {?} } $
Answer: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{5}\times{2} & {5}\times{0} & {5}\times{4} \\ {5}\times{1} & {5}\times{4} & {5}\times{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{10} & {0} & {20} \\ {5} & {20} & {-5}\end{array}\right]}$